The use of fiber optics in control systems offers many operational advantages over similar electrical devices. Fiber optic circuits are electrically passive, operating only with light. As such they offer unprecedented safety, immunity to noise, and ease of installation, all of which translate into lower costs and increased reliability. Physical design requirements are greatly simplified since fiber optic cables and components can be located adjacent to existing electrical installations without regard to interference from the electrical system or interaction between the two systems. Accordingly, fiber optic coupled sensors and switches are used in many industrial, commercial and residential applications.
Generally, fiber optic circuits require a fiber optic driver. A typical fiber optic driver includes, as a minimum, a source of light, a detector of light and electronic circuitry to process the light signal being detected and to determine the state of the fiber coupled device being driven. Drivers may provide an output interface and additional functions such as background compensation or noise filtering.
It is possible to make a multiple channel driver by simply packaging multiple single channel drivers together. However, this results in several undesirable consequences. Two primary problems are channel crosstalk and peak power demands.
Channel crosstalk occurs when multiple independent drivers operate with modulation frequencies or synchronization times that are sufficiently close that their detection circuits cannot distinguish them. As a result, inaccurate switching can occur.
The optical sources typically used in fiber optic coupled drivers consume most of the electrical power. When independent devices are used, many of the fiber optic sources may be operated at the same time. Accordingly, the power supply must be designed to meet the current demands of multiple sources activated simultaneously. It is desirable to provide the benefits of a multiple channel driver while avoiding the limitations of the prior art systems.